This invention relates to earth working plows, and more particularly to a plow assembly in which each plow bottom is biased retractably outward to ground working position for inward deflection upon engagement with an obstacle in the ground.
Retractable plow bottoms of the class described are disclosed in U.S. Pat. No. 3,662,840 wherein opposed pairs of plow bottoms are interconnected by an extensible hydraulic piston-cylinder unit which communicates at one end with a source of hydraulic fluid under pressure, such as an accumulator or a tractor hydraulic system. However, when the supply of hydraulic pressure is an accumulator, the opposite end of each piston-cylinder unit communicates with the atmosphere. Accordingly, with the use of conventional, inexpensive piston-cylinder units wherein the piston rod is much smaller in diameter than the piston and cylinder bore operation of the unit functions to draw into the cylinder thereof dust and other debris carried by the air in proximity to the operating plow assembly. The accumulation of such debris in the cylinder results in excessive and premature wear, damage, or other malfunctioning of the unit, requiring frequent replacement or repair. The patent referred minimizes this result by utilizing expensive piston-cylinder units in which the piston and piston rod have substantially the same diameter as the cylinder bore. When the supply of hydraulic pressure is the hydraulic system of a tractor, the opposite end of each piston-cylinder unit must be supplied with a long conduit for communicating it with a sump associated with a hydraulic system. This represents a costly duplication of hydraulic lines and fittings, and doubles the possibility of line breakage or their damage, with consequent malfunctioning of the system.